A Welsh Government spokesman said: “Against the backdrop of cuts made to the Welsh block by the UK Government it is important we assess our spending priorities carefully and will consider what action may be necessary once the full details are known.”

July’s RPI inflation figure, on which the January rise in season tickets is based, is being published today by the Office for National Statistics.

The current annual price-rise formula is for regulated fares, which include season tickets, to rise by the rate of RPI plus 1%, which could see average fares going up around 3.6% if RPI remains at its June 2014 level of 2.6%.

Train companies also have a “flex” rule which allows them to raise some regulated fares by 2% above the average as long as the overall average remains at the RPI plus 1% level. This means some fares could go up by around 5.6% in the new year.

In his 2013 autumn statement Chancellor George Osborne announced he was limiting the January 2014 regulated-fare rise to RPI plus 0% while reducing the “flex” rule from 5% to 2%. This kept the average increase in regulated fares to 3.1%.

CBT public transport campaigner Martin Abrams said: “With people’s wages stagnating and in some cases falling the expense of taking the train to work has become a huge part of living costs. If the government doesn’t put an end to above-inflation fare increases quickly ordinary commuters will be priced off the train and could be forced into agonising decisions such as moving house or quitting their jobs.”